The weight of a fluid often needs to determined based on the measured level of the fluid in a tank or other container. The fluid weight is often determined by measuring the dielectric constant of the fluid, and calculating the fluid density based on a known relationship between the dielectric constant and density for the particular fluid. The density can be used to calculate the weight of the fluid based on the volume of fluid in the tank. The volume of fluid can be calculated based on the measured fluid level.
The dielectric constant of a fluid is typically measured using an electrical sensor immersed in the fluid. The use of an electrical sensor for this task can present substantial disadvantages. For example, the introduction of electrical current into a tank of fluid can generate an explosion hazard. In particular, the electrical current has the potential to introduce a spark within the tank due to, for example, chaffed insulation on the wiring associated with the dielectric current sensor. A spark can ignite explosive vapors that may be present in the tank.
For example, Jet A fuel used by commercial aircraft has a flash point of about 38° C. Thus, sufficient vapors may be present in a tank of Jet A fuel under normal operating conditions to cause an explosion if a spark is present within the tank.
Electrical sensors are susceptible to signal degradation in the presence of electromagnetic interference. Moreover, electrical sensors, when used to measure fuel levels, can lose accuracy as the amount of water and other contaminants in the fuel increases.
An ongoing need therefore exists for a system that can determine the density of a fluid in a tank or other container without introducing electrical current into the tank or container, and that can function in a satisfactory manner in the presence of contaminates and/or electromagnetic interference.